It has been known that the addition of a filler to a matrix such as a resin imparts properties such as electric conductivity, thermal conductivity and antistatic properties. Since some carbon fibers exhibit high conductivity, the effect of imparting electric conductivity can be expected. For example, Patent Document 1 discloses that an electrode for a lithium ion battery is allowed to contain a fibrous carbon having a diameter of less than 100 nm, and a fibrous carbon having a diameter of 100 nm or more and/or a non-fibrous conductive carbon as conductive materials.